I think it has something to do with the service (Ticketbud) being connected to Paypal? It's sometimes really picky about credit card histories, like for example, I used my mom's card, and it declined it, but I used my dad's card, which is connected to paypal, and it accepted it with no trouble.
I might be wrong, but that was my experience.
I'm more concerned that my badge hasn't arrived from when I ordered it in June.